Heat exchangers are wall constructions which include means for facilitating thermal transfers between two or more fluids circulating about the wall construction. A review of the relevant prior art has unveiled the following patents:
U.S. Pat. No. 2,281,754 to Dalzell;
U.S. Pat. No. 1,826,344 to Dalgliesch;
U.S. Pat. No. 3,473,604 to Tiefenbacher;
U.S. Pat. No. 3,783,090 to Andersson et al;
U.S. Pat. No. 4,293,033 to Nasser;
U.S. Pat. No. 4,470,453 to Laughlin et al;
U.S. Pat. No. 4,569,391 to Hulswitt et al;
Canadian patent No. 592,566 to Andre Huet;
Canadian patent No. 1,098,113 to Davidson.
These patented heat exchangers are made up of a plurality of plates or sheets which are dimpled in a manner to provide tortuous paths for one liquid in one direction, and tortuous paths in adjacent plates for a second liquid in a second direction transverse or perpendicular to that of the first liquid. Hence, undulating "tubes" are formed.
More specifically, in U.S. Pat. No. 4,293,033 (dated Oct. 6, 1981), there is provided a stack of heat exchanger plates formed by corrugated plates 1, 2, which lie against one another, and form a plate pair (FIG. 2). Each pair of plates 1, 2 define transverse tubular passages 3 which are separated by the thickness of the plates from longitudinal undulating flow passages 4. A bar 5 separates each two pairs of successively superimposed pairs of plates 1, 2. Because of the spacer bars, the required volume to store this heat exchanger wall construction before use remains substantial, and also this construction cannot be easily disassembled/reassembled.
In U.S. Pat. No. 4,569,391 (dated Feb. 11, 1986) is an improvement relative to U.S. Pat. No. 4,293,033, since no spacer bar is required. In this more recent patent, there is provided a number of plates 30-36, each having a plurality of protuberances 40-46 projecting from one side only of the corresponding plate. In some plates, the protuberances are all directed downwardly, and so constitute depressions. Space use is thus more efficient than in the 1981 patent, but, in the opinion of the present inventors, this wall construction could still be improved with respect to the capacity of reduction of volume for storage before use.